fix: disable nginx buffering for streaming responses

- Add X-Accel-Buffering: no header to prevent nginx from buffering streamed content
- Ensures immediate delivery of each chunk without proxy buffering delays
- Improves real-time streaming performance and responsiveness
- Applies to both production and local Dockerfiles

Dockerfile.base

@@ -71,6 +71,7 @@ RUN printf '%s\n' \
 '        proxy_request_buffering off;' \
 '        chunked_transfer_encoding on;' \
 '        gzip off;' \
+'        add_header X-Accel-Buffering no;' \
 '        proxy_connect_timeout 600s;' \
 '        proxy_send_timeout 600s;' \
 '        proxy_read_timeout 600s;' \